Aw: RE: [OpenAFS] compile fails kernel version 4.4.0-1-default

Benjamin Kaduk kaduk@MIT.EDU
Mon, 7 Mar 2016 22:37:26 -0500 (EST)

  This message is in MIME format.  The first part should be readable text,
  while the remaining parts are likely unreadable without MIME-aware tools.

Content-Type: TEXT/PLAIN; charset=UTF-8
Content-Transfer-Encoding: QUOTED-PRINTABLE

On Mon, 7 Mar 2016, Chas Williams wrote:

> On Mon, 2016-03-07 at 01:42 -0500, Benjamin Kaduk wrote:
> >
> > I am given to understand that the proximal trigger is linux commit
> >
> > ?id=3Dc725bfce7968009756ed2836a8cd7ba4dc163011,
> > which addds a path wherein -ERESTARTSYS can be returned from within
> > VFS
> > library code.=C2=A0 (Maybe there are other such paths, but we maybe jus=
> > didn't
> > notice before?)=C2=A0 This particular function, splice_from_pipe_next()=
> > ends
> > up getting called from the low-level afs_linux_storeproc() routine.=C2=
> I haven't had time to look at this, but does this also happen with
> the memcache?

I believe so.

> > There
> > are many call paths in the cache manager that end up at this function,
> > most of which are not prepared to properly handle an ERESTARTSYS
> > return.
> > Since this status can be returned after some data has already been
> > written, the correct behavior upon receiving it is far from clear ...
> > a
> > path towards a client free of this vector for data corruption may
> > involve
> > avoiding the dependence on splice_from_pipe_next() in preference to
> > adopting all call sites to handle the ERSTARTSYS case.
> For the 1.6 release, this seems the best choice of action. =C2=A0The "rea=
> fix would likely be difficult to completely test in a timely fashion.

That only helps if we know what the replacement would be...I am not a
linux VFS expert and do not have any ideas right now.